Estimating Rice Leaf Greenness (SPAD) Using Fixed-Point Continuous Observations of Visible Red and Near Infrared Narrow-Band Digital Images

Abstract

A narrow-band dual camera system demonstrated a new close-range sensing technique to seasonally track trends in leaf greenness in rice paddies. A weatherproof digital imaging system for the visible red (RED, 620?650 nm) and near infrared band (NIR, 820?900 nm) was positioned 12 m above a 600-m² rice field. During the 2009 and 2010 paddyrice seasons, the system automatically logged images at 10-min intervals throughout the day. Radiometric corrections for the images utilized solar irradiance sensors and prior calibration to calculate 0900-1500 JST daily-averaged reflectance factors (DARF). The DARF in RED (DARF-RED) and NIR (DARF-NIR) values were transformed to provide a daily-averaged normalizeddifference vegetation index (DA-NDVI). The DA-NDVI increased more rapidly in the vegetative growth period, and reached an asymptotic plateau earlier than the DARF-NIR. From transplanting to harvest, leaf greenness values (measured by the SPAD index) were measured for the central part of the uppermost leaves of targeted canopies weekly with a chlorophyll meter. We developed a leaf greenness index (LGI), the ratio of DA-NDVI to DARF-NIR, and a simple calculation method for area means to reduce the background effect. The modified area means of LGI followed the seasonal trend in SPAD value well; its patternwas inherently different from the patterns of any of the original three parameters: DARF-RED, DARF-NIR or DA-NDVI. Throughout the paddy seasons in the two years, a regression equation for estimating SPAD values using the LGI, daily solar radiation, the cosine of angle between the view and the meridian directions and the cosine of culmination solar zenith angle performed favorably (R²=0.815). The nitrogen concentration per dry plant hill (g kg-¹) had a close relation to the SPAD values estimated using the equation.     

Regression-Based Models to Predict Rice Leaf Area Index Using Biennial Fixed Point Continuous Observations of Near Infrared Digital Images

Abstract

A weatherproof digital imaging system for the near infrared band (NIR, 820–900 nm) was positioned 12 m above a 600-m² rice field. During the 2008 and 2009 paddy rice seasons, the system automatically logged images at 10-min intervals throughout the day. Radiometric corrections for the NIR images utilized a solar irradiance sensor and prior calibrations to calculate 0900–1500 JST daily-averaged reflectance factors (DARF). Prior to heading, empirically derived equations for predicting leaf area index (LAI) using the 2008 DARF values in NIR, the cosines of angles between the view and the planting row directions, and between the view and the meridian directions were verified with the 2009 data set. Transformation of a model variable by arcsine square root function improved the performance of the LAI prediction by reducing the errors and bias at low LAI values. Adding variables to incorporate lateral angular components to the horizontal viewing angular parameters hardly affected the overall performance of the models and did not reduce variation. This was probably because the height and position of the camera system were the same in successive years. In-plot means of two or four predicted values in each plot reduced the root-mean square error 30%. These results indicate that radiometric NIR images derived using a fixed-point observation system can accurately predict LAI and the simple multiple linear regression equations developed for a given year can be used the following year without in-situ recalibration.     

Analysis of Common Canopy Reflectance Spectra for Indicating Leaf Nitrogen Concentrations in Wheat and Rice

Abstract

Non-destructive monitoring and diagnosis of plant nitrogen (N) concentration are of significant importance for precise N management and productivity forecasting in field crops. The present study was conducted to identify the common spectra wavebands and canopy reflectance spectral parameters for indicating leaf nitrogen concentration (LNC, mg N g-¹ DW) and to determine quantitative relationships of LNC to canopy reflectance spectra in both rice (Oryza sativa L.) and wheat (Triticum aestivum L.). Ground-based canopy spectral reflectance and LNC were measured with seven field experiments consisting of seven different wheat cultivars and five different rice cultivars and varied N fertilization levels across three growing seasons for wheat and four growing seasons for rice. All possible ratio vegetation indices (RVI), difference vegetation indices (DVI), and normalized difference vegetation indices (NDVI) of key wavebands from the MSR16 radiometer were calculated. The results showed that LNC of wheat and rice increased with increasing N fertilization rates. Canopy reflectance, however, was a more complicated relationship under different N application rates. In the near infrared portion of the spectrum (760?1220 nm), canopy spectral reflectance increased with increasing N supply, whereas in the visible region (460?710 nm), canopy reflectance decreased with increasing N supply. For both rice and wheat, LNC was best estimated at 610, 660 and 680 nm. Among all possible RVI, DVI and NDVI of key bands from the MSR16 radiometer, NDVI(1220, 610) and RVI(1220, 610) were most highly correlated to LNC in both wheat and rice. In addition, the correlations of NDVI(1220, 610) and RVI(1220, 610) to LNC were found to be higher than those of individual wavebands at 610, 660 and 680 nm in both wheat and rice. Thus LNC in both wheat and rice could be indicated with common wavebands and vegetation indices, but separate regression equations are necessary for precisely describing the dynamic change patterns of LNC in wheat and rice. When independent data were fit to the derived equations, the root mean square error (RMSE) values for the predicted LNC with NDVI(1220, 610) and RVI(1220, 610) relative to the observed values were 10.50% and 10.52% in wheat, and 13.04% and 12.61% in rice, respectively, indicating a good fit. These results should improve the knowledge on non-destructive monitoring of leaf N status in cereal crops.     

Response of Spikelet Number per Panicle in Rice Cultivars to Three Transplanting Densities

Abstract

Spikelet number per panicle (SPP), differentiated spikelet number per panicle (D-SPP), and preflowering aborted spikelet number per panicle (A-SPP) were examined in five rice cultivars at three planting densities (HD; high, MD; medium, LD; low planting density) in the field condition. Rice plants at LD produced a higher panicle number per plant but lower panicle number per unit area, accompanied by higher D-SPP and SPP, on average. A-SPP and the ratio of A-SPP to D-SPP (%A) showedno consistent trends. There was a broader range of D-SPP values at LD than at HD because of larger D-SPP in higher order panicles (panicles with a higher spikelet number). D-SPP was smaller in lower order panicles in all cultivars and years, whereas %A increased. D-SPP and SPP of each panicle were positively correlated with tiller size (tiller height, leaf area, and neck internode diameter). Spikelet production efficiency for D-SPP or for SPP (spikelet number per leaf area) of each tiller was higher in IR65564-44-51 (NPT65) and Akihikari than in the other cultivars, indicating a greater capacity of tillers to produce spikelets or support spikelet growth. In each cultivar except NPT65, spikelet production efficiency for D-SPP increased as panicle order decreased, whereas spikelet production efficiency for SPP remained constant or decreased. This finding indicates that irrespective of planting density, lower order panicles produce more spikelets than they can afford physiologically, but they were regulated downward to a nearly constant value in four cultivars. In NPT65 different from other cultivars, spikelet production efficiency for D-SPP was lower in lower order panicles.     

The estimation of dry green biomass in hayfields from canopy spectroreflectance measurements

Spectral reflectance measurements were found useful in estimating the dry green biomass (DGB) in hayfields in eastern Québec, Canada. The calibrated measurements of reflectance obtained in the 650 and 800 nm bands (respectively defined as the RED and NIR indices), the NIR/RED ratio, and the ratio (NIR-RED)/(NIR + RED) were used to generate various regression models which explained between 74 and 90% of the variance in DGB. The proportion of legumes, grasses and herbs in the canopy had no apparent influence on the reflectance measurements or on the value of the models.     

Yield formation and tillering dynamics of direct-seeded rice in flooded and nonflooded soils in the Huai River Basin of China

Water shortage in the Huai River Basin prompts farmers to adopt water-saving technologies such as direct-seeded nonflooded or aerobic rice. Different cultivation practices impact on tiller growth and development. Improved insight into tiller dynamics is needed to increase yield in these production systems. We conducted field experiments with four direct-seeded rice varieties under flooded and nonflooded conditions in Mengcheng county, Anhui province, in 2005–2006. The soil water content in the nonflooded treatment varied between saturation and field capacity. Yields in nonflooded soil ranged from 3.6 to 4.7 t ha⁻¹, and did not differ significantly from yields in flooded soil that ranged from 3.6 to 5.1 t ha⁻¹. Variety had a significant effect on biomass, yield, panicle number, spikelet number, grain weight, and grain filling percentage. Panicle number was the main factor limiting yield, resulting from a low tiller emergence frequency and a low fraction of productive tillers in both the flooded and the nonflooded soils. On average, the panicle number was 159–232 m⁻², including 34–167 productive tillers per m² for all the varieties under the two water regimes. The contribution of productive tillers to yield varied between 7% and 47%. There were two peaks of tillers that contributed to yield, one at the low (4th or 5th) and one at the high (10th or 11th) phytomer orders. Frequencies of tiller emergence at most phytomer orders were higher in the flooded soil than in the nonflooded soil. There were no significant differences in frequencies of productive tiller emergence and contributions to yield from tillers between the soil water regimes for three of the four tested varieties. To increase yield in direct-seeded nonflooded rice production systems, both the tiller emergence frequency and the fraction of productive tillers should increase through breeding, improved crop management, or a combination.     

Canopy Spectral Reflectance Characteristics of Rice with Different Cultural Practices and Their Fuzzy Cluster Analysis

The influence of major cultural practices including different nitrogen application rates, population densities, transplanting leaf ages of seedling, and water regimes on rice canopy spectral reflectance was investigated. Results showed that increased nitrogen rates, water regimes and population densities and decreased seedling ages could enhance reflectance at NIR (near infrared) bands and reduce reflectance at visible bands. Using reflectance of green, red and NIR band and ratio index of 810-560 nm could distinguish the different type of rice by fuzzy cluster analysis.     

Relationship between Dry Weight at Heading and the Number ofSpikelets on Individual Rice Tillers

Abstract

The objectives of this study were to identify the growth parameters involved in determining the number of spikelets on an individual tiller (ST) and to elucidate how ST is determined in rice (Oryza sativa L.). We examined the correlation of ST with the dry weight (DWT), leaf area (LAT), and the amount of nitrogen (NT) at heading for individual tillers grown under different conditions that were expected to affect spikelet production. In 1999, the japonica rice cultivars “Mineasahi” (short-duration), “Hinohikari” (intermediate-duration), and “Akebono” (long-duration) were transplanted in a paddy field on two different dates (EARLY and LATE). In 2000, Hinohikari was grown under three different treatments (gibberellic acid application, nitrogen topdressing, and thinning of hills at panicle initiation) and without treatment (control). Covariance and partial correlation analyses indicated that ST was positively and essentially correlated with DWT rather than with LAT and NT. The regression of ST on DWT was stable within each cultivar regardless of the treatment, year, tiller order, and number of differentiated spikelets. The slope of the regression was the steepest in the short-duration cultivar. These results suggest that the steep slope is desirable for high-yielding cultivars with large panicles. We conclude that ST is mostly determined by dry matter production of an individual tiller regardless of the number of differentiated spikelets. We present a diagram showing the relationship between dry matter production and the number of differentiated, surviving, and degenerated spikelets on an individual tiller.     

Yield formation of CO2-enriched hybrid rice cultivar Shanyou 63 under fully open-air field conditions

Hybrid indica rice (Oryza sativa L.) cultivars play an important role in rice production system due to its heterosis, resistance to environmental stress, large panicle and high yield potential. However, no attention has been given to its yield responses to rising atmospheric [CO₂] in conjunction with nitrogen (N) availability. Therefore we conducted a free air CO₂ enrichment (FACE) experiment at Yangzhou, Jiangsu, China (119°42′0′′E, 32°35′5′′N), in 2004–2006. A three-line hybrid indica rice cv. Shanyou 63 was grown at ambient and elevated (ca. 570 μmol mol⁻¹) [CO₂] under two levels of supplemental N (12.5 g Nm⁻² and 25 g Nm⁻²). Elevated [CO₂] had no effect on phenology, but substantially enhanced grain yield (+34%). The magnitude of yield response to [CO₂] was independent of N fertilization, but varied among different years. On average, elevated [CO₂] increased the panicle number per square meter by 10%, due to an increase in maximum tiller number under enrich [CO₂], while productive tiller ratio remained unaffected. Spikelet number per panicle also showed an average increase of 10% due to elevated [CO₂], which was supported by increased plant height and stem dry weight per tiller. Meanwhile, elevated [CO₂] caused a significant enhancement in both filled spikelet percentage (+5%) and individual grain weight (+4%). Compared with the two prior FACE studies on rice, hybrid indica rice cultivar appears to profit much more from elevated [CO₂] than japonica rice cultivar (ca. +13%), not only due to its stronger sink generation, but also enhanced capacity to utilize the carbon sources in a high [CO₂] environment. The above data has significant implication with respect to N strategies and cultivar selection under projected future [CO₂] levels.     

Path Analysis of Tiller Density of Winter Wheat Demonstrates the Importance of Practices that Manipulate Clod Size Based on Soil Moisture at Seeding in the Rice–Wheat Cropping System

Abstract

The moisture of paddy soil after rice cropping is a major impediment to the establishment, tillering and yield of winter wheat in the rice?wheat (R?W) cropping system. We examined the seedling establishment ratio, based on soilmoisture at seeding by path analysis of nine soil/plant traits in the farmer's fields in Western Japan where the R?W cropping system was being used, to establish a strategy for improving tiller density by optimizing the seedling establishment ratio. The clod size of surface soil, which showed a significant positive correlation with soil moisture at seeding, had a significant negative direct effect on the seedling establishment ratio. The reduction in seedling establishment ratio, together with fewer tillers per plant, resulted in a significant decrease in tiller density. The sum total of contribution of soil moisture contents to tiller density via clod size was smaller than that of seeding rate, and similar to that of the amount of nitrogen (N) basal dressing. This indicates that manipulating clod size based on soil moisture at seedingprovides an opportunity for maintaining tiller density, as well as changing the amount of N basal dressing with the soil moisture conditions after rice cropping.     

10种除草剂对武育粳3号生长及“小粒穗”形成的影响

 采用盆栽试验研究了10种除草剂对水稻生长及对“小粒穗”形成的影响。 在土壤处理中,用药处理后10、20 d,乙草胺225、337.5 g/hm2处理和乙草胺225 g/hm2+苄嘧磺隆22.5 g/hm2混用处理显著地 (P=0.05)抑制水稻株高,但并不影响分蘖发生,到用药后40 d,土壤处理药剂处理的水稻株高与对照无显著差异;在处理后10、20 d, 氯磺隆0.375、0.75、1.5 g/hm2处理可显著(P=0.05)影响水稻株高,而甲磺隆0.75、1.5 g/hm2处理在用药后30、40 d仍显著影响水稻株高,氯磺隆1.5 g/hm2和甲磺隆0.75、1.5 g/hm2在药后10、20 d也显著地影响水稻茎蘖数,但在药后40 d两药剂处理与对照均无显著差异。茎叶处理中,药剂处理对水稻株高、分蘖产生无显著的抑制作用。同时, 除草剂处理基本上不对水稻结实性产生影响,并未发现典型的“小粒穗”,表明稻田使用除草剂不是引起水稻“小粒穗”的直接原因。     

Varietal differences in tiller and panicle development determining the total number of spikelets per unit area in rice

ABSTRACT

Rice varietal differences were compared between japonica type (JAT) and indica type (INT) and between panicle number type (PNT) and panicle weight type (PWT) in terms of tiller and panicle development. Rice varieties PNT-JAT Hinohikari, PWT-JAT Akenohoshi, PNT-INT IR36, and PWT-INT Takanari were used in the field experiments. Tiller bud formation and tiller leaf emergence occurred slightly later in the PWT than in the PNT varieties. These parameters occurred slightly earlier in the INT than in the JAT varieties. The maximum number of tillers was greater in IR36 than in Takanari, Hinohikari, and Akenohoshi. The number of panicles per unit area (PN) was greater in IR36 and Hinohikari than in Akenohoshi and Takanari. The widths of the shoot apical meristem (SAM) just before panicle initiation were in the order of Akenohoshi > Hinohikari = Takanari > IR36. The number of spikelets per panicle (SN) was in the order of Takanari = Akenohoshi > IR36 > Hinohikari. In conclusion, the PWT varieties, which had relatively wider SAM, presented with the promotion of main shoot development and the suppression of tiller development. Consequently, PN decreased and SN increased in PWT varieties. INT varieties presented with the promotion of tiller and rachis branch development, which resulted in increases in both PN and SN. These developmental factors may determine varietal differences in the total number of spikelets per unit area.     

Morphological analysis on comparison of organic and chemical fertilizers on grain quality of rice at different planting densities

ABSTRACT

Effects of organic (Italian ryegrass and Bokashi) and chemical fertilizer on growth, yield, and grain quality of rice (Oryza sativa L.) were compared under different planting densities in 2013/2014 and 2014/2015. Italian ryegrass was incorporated into the soil as green manure. Bokashi (a mixture of organic materials) was applied as basal dressing. To measure yield and its components, 30 hills were chosen for each treatment. Rice grains were harvested from each treatment to assess the grain quality and to evaluate accumulation structures using a scanning electron microscope. Bokashi treatment increased panicle number per hill, ripened grain percentage, panicle number per m², and grain yield compared to no fertilizer treatment at normal planting density. Chemical fertilizer treatment increased plant length at high planting density. Italian ryegrass and Bokashi treatments promoted the taste point (taste score as reference) by reduction of amylose and protein contents at normal planting density in contrast to chemical fertilizer. 1000-grain weight, panicle number per m², and grain yield were higher at high planting density than at normal planting density. However, high planting density decreased panicle number per hill and spikelet number per panicle. It also enhanced the amylose content of rice grain. Scanning electron microscopic observation revealed that chemical fertilizer treatment marked up protein bodies and their traces on amyloplasts. However, Bokashi treatment produced large amyloplasts, which included many starch granules. These results show that Italian ryegrass and Bokashi can offset reductions of chemical fertilizer and can lead to sufficient starch accumulation structures in rice grains.     

Effects of Elevated Atmospheric Carbon Dioxide Concentration on Silica Deposition in Rice (Oryza sativa L.) Panicle

Abstract

The effects of elevated carbon dioxide concentration ([CO₂]) on silica deposition on husk epidermis of rice (Oryza sativa L. cv. Akitakomachi) during the flowering stage were investigated in this study. The study was motivated by the concept that the rice yield maybe affected by global warming as a result of elevated [CO₂] environment since sterility of rice is related to the panicle silica content that influences transpiration, and elevated [CO₂] could affect plant transpiration. Silica deposition analysis was focused on the flowering stage of the rice crop grown hydroponically under two [CO₂] conditions: 350 μmol mol-¹ (ambient) and 700 μmol mol-¹ (elevated). Silica deposition on the husk epidermis from three parts of the panicle at four flowering stages were examined using a scanning electron microscope (SEM) combined with an energy dispersive X-ray microanalyzer (EDX). The results demonstrated that elevated [CO₂] significantly suppressed silica deposition on the husk epidermis at the lower part of the panicle, and at the early flowering stage when 1/3 of the panicle emerged from the leaf sheath. In the transverse section analysis of the husk, silica deposition on the husk epidermis under elevated [CO₂] was less than that under ambient [CO₂] at the late flowering stage. The less silica deposition observed on the husks at the late flowering stage under elevated [CO₂] might be related to the suppressed transpiration from the panicle by elevated [CO₂] found in a previous study.     

New Vegetation Index and Its Application in Estimating Leaf Area Index of Rice

Leaf area index (LAI) is an important characteristic of land surface vegetation system, and is also a key parameter for the models of global water balancing and carbon circulation. By using the reflectance values of Landsat-5 blue, green and red channels simulated from rice reflectance spectrum, the sensitivities of the bands to LAI were analyzed, and the response and capability to estimate LAI of various NDVIs (normalized difference vegetation indices), which were established by substituting the red band of general NDVI with all possible combinations of red, green and blue bands, were assessed. Finally, the conclusion was tested by rice data at different conditions. The sensitivities of red, green and blue bands to LAI were different under various conditions. When LAI was less than 3, red and blue bands were more sensitive to LAI. Though green band in the circumstances was less sensitive to LAI than red and blue bands, it was sensitive to LAI in a wider range. When the vegetation indices were constituted by all kinds of combinations of red, green and blue bands, the premise for making the sensitivity of these vegetation indices to LAI be meaningful was that the value of one of the combinations was greater than 0.024, i.e. visible reflectance (VIS)>0.024. Otherwise, the vegetation indices would be saturated, resulting in lower estimation accuracy of LAI. Comparison on the capabilities of the vegetation indices derived from all kinds of combinations of red, green and blue bands to LAI estimation showed that GNDVI (Green NDVI) and GBNDVI (Green-Blue NDVI) had the best relations with LAI. The capabilities of GNDVI and GBNDVI to LAI estimation were tested under different circumstances, and the same result was acquired. It suggested that GNDVI and GBNDVI performed better to predict LAI than the conventional NDVI.     

湖北稻茬小麦主茎、分蘖1、分蘖2和分蘖3的成穗率、产量贡献率及主要农艺性状分析

合理的茎蘖组合是提升小麦绿色高效生产的重要因素。为了解湖北稻茬小麦主要茎蘖对产量及主要农艺性状的影响,以大穗型小麦品种川麦104和多穗型小麦品种扬麦15为材料,于2016-2018年在湖北十堰和武汉两地稻茬麦大田条件下,设置低(1.35×106~1.65×106株·hm^-2)、中(2.85×106~3.15×106株·hm^-2)、高(4.35×106~4.65×106株·hm^-2)三种种植密度,分析了主茎(S)、分蘖1(T1)、分蘖2(T2)和分蘖3(T3)(按出现先后顺序)的成穗率、产量贡献率及相关农艺性状的表现。结果表明:(1)湖北稻茬小麦成穗茎蘖农艺性状表现值偏低,除穗长和茎高受品种的影响最大外,其他被测性状受影响程度表现为蘖位>种植密度>品种;(2)在主茎均能成穗的情况下,分蘖成穗率随蘖位和种植密度的升高而降低,大穗型品种川麦104的降幅大于多穗型品种扬麦15;(3)主茎产量贡献率随种植密度的升高而升高(35.12%~54.50%),分蘖1产量贡献率稳定在23.25%~25.50%,分蘖2和分蘖3的产量贡献率随种植密度升高而降低,分别为14.59%~23.22%和5.42%~16.77%;(4)主茎的穗粒数(35.94~44.13粒)和穗粒重(1.44~1.93 g)显著高于其分蘖,茎高、茎蘖收获指数和穗茎节长只在川麦104中、高种植密度下的分蘖3与其他茎蘖差异显著;穗长、可孕小穗数和不孕小穗数有随蘖位和种植密度升高而变劣的趋势。聚类分析得出:湖北稻茬小麦绿色高效生产模式,以主茎成穗为主体,低种植密度下增加分蘖1和分蘖2,争取分蘖3成穗为辅;中种植密度下争取分蘖1+分蘖2成穗为辅;而高种植密度下争取分蘖1成穗为辅。     

不同类型水稻品种产量和氮素吸收利用对大气CO2浓度升高响应的差异

目的 探明不同类型水稻品种产量和氮素吸收利用对FACE(大气CO₂浓度增高)响应的差异。方法 以常规粳稻、杂交籼稻、常规籼稻共6个品种为供试材料,研究FACE对不同类型水稻产量、氮素吸收利用的影响。结果 1）FACE处理极显著提高了水稻产量,平均增加24.17%, 常规籼稻增幅最大,FACE和对照均以杂交籼稻最高;2）FACE处理显著增加了单位面积穗数,常规粳稻增幅最大,并显著增加了杂交籼稻和常规籼稻每穗粒数;3）FACE处理显著提高了成熟期吸氮量和氮素籽粒生产效率,成熟期吸氮量平均增加21.23%,杂交籼稻增幅最大, FACE和对照均以常规籼稻最高;氮素籽粒生产效率平均增加7.33%,杂交籼稻增幅最大,FACE和对照均以杂交籼稻最高。成熟期吸氮量对产量促进作用略大于成熟期氮素籽粒生产效率;4）FACE处理降低了植株含氮率,成熟期平均下降0.105个百分点,常规粳稻降幅最大。FACE处理极显著提高植株干物质量,成熟期平均增加23.95%,常规籼稻增幅最大;FACE处理显著提高常规籼稻和杂交籼稻成熟期单穗吸氮量,分别增加10.79%、13.93%,但常规粳稻下降了9.60%;FACE处理显著提高了成熟期群体吸氮强度,平均增加22.29%,杂交籼稻增幅最大。FACE处理对水稻全生育期天数无显著影响;FACE处理显著提高茎鞘、叶片、穗各器官吸氮量,叶片增幅最大,平均增加51.86%,杂交籼稻增幅最大;FACE处理显著提高了不同生育阶段吸氮量,抽穗-成熟阶段增幅最大,平均增加108.90%,杂交籼稻增幅最大;5）植株干物质量、单穗吸氮量、吸氮强度、穗吸氮量、抽穗-成熟阶段吸氮量对成熟期总吸氮量的促进作用分别大于植株含氮率、单位面积穗数、生育天数、茎鞘叶吸氮量、移栽-分蘖和分蘖-抽穗阶段吸氮量;6）FACE处理显著提高了氮肥偏生产力,降低了每百千克籽粒需氮量,前者平均增加24.16%,常规籼稻增加最多;后者平均降低4.7%,常规籼稻降幅最大。结论 FACE处理可显著提高水稻产量和氮素吸收利用效率,但品种间差异较大。     

膜下滴灌栽培粳稻品种产量构成与穗部特征研究

为探讨膜下滴灌栽培模式下的粳稻产量构成及其穗部特征,以12个水稻品种(A1~A12)为材料,比较分析了其产量及其构成因素、茎蘖组成及其成穗率、穗部构成特征.结果表明:在膜下滴灌栽培条件下,不同品种的产量及其构成因素平均值以A6最高,膜下滴灌水稻主要依靠主茎和一级分蘖成穗,且主茎和一级分蘖的贡献率占97%以上,群体数量的上升较平稳,成穗率中等;膜下滴灌水稻可以依靠二次枝梗数来增加穗粒数,二次枝梗对穗粒数的贡献率在57%以上.膜下滴灌水稻栽培应选用着粒密度较大、紧实的大穗型品种.     

Differences in Response of Grain Yield,Nitrogen Absorption and Utilization to Elevated CO2 Concentration in Different Rice Varieties

【Objective】Our aim is to investigate the differences in response of grain yield, nitrogen absorption and utilization to FACE (atmospheric CO2 concentration increase) of different rice varieties. 【Method】Six rice varieties, including conventional japonica rice, hybrid indica rice, and conventional indica rice, were used to study the effects of free-air CO2 enrichment (FACE) (atmospheric CO2 concentration increase) on the nitrogen absorption, utilization, and yield of different types of rice.【Result】 1) FACE treatment dramatically increased rice yield by 24.17% on average and the maximum increment was observed in conventional indica rice. Compared with other types of rice varieties, hybrid indica showed the highest grain yield under both FACE and control (CK) treatments. 2) Panicle number was significantly improved in FACE treatment with conventional japonica rice varieties having the maximum increment. Spikelet number per panicle was significantly improved in hybrid and conventional indica rice varieties in FACE treatment. 3) The nitrogen absorption (NA) and nitrogen use efficiency for grain yield (NUEg) were significantly higher in FACE treatment than those in CK treatment. The average increase of NA was 21.23% with the maximum increment in hybrid indica rice varieties. Compared with other rice varieties, conventional indica rice varieties had the highest NA both in FACE and CK treatments. The average increase of NUEg was 7.33% with hybrid indica rice varieties enjoying the maximum increment. The hybrid indica rice varieties had the highest NUEg in FACE treatment and in CK treatment, respectively. 4) Nitrogen content was decreased in FACE treatment with the average decrease of 0.105%, among which the maximum decrease was observed in conventional japonica rice. Dry matter weight was extremely and significantly increased in FACE treatment. The average increase of dry weight was 23.95% with the maximum increment in conventional indica rice varieties. NA of single panicle was significantly improved in FACE treatment with the average increase of 10.79% in conventional indica rice varieties and 13.93% in hybrid indica rice varieties, but NA of single panicle was decrease by 9.60% in conventional japonica rice. FACE treatment significantly increased rice NA intensity with an average increase of 22.29% and the maximum increment was observed in hybrid indica rice varieties. The growth duration was not influenced by FACE treatment in all rice varieties. NAs of stem, leaf and panicle were significantly higher in FACE treatment than in CK treatment with the highest increase of 51.86% in leaf. The largest increase of NA was observed in hybrid indica rice. NA in different rice growth stages was significantly improved with the maximum increment of 108.90% during heading-maturity. The maximum increment of NA from heading to maturity was observed in hybrid indica rice varieties.5) Effects of dry matter weight, NA per panicle, NA intensity, NA of panicle and NA from heading to maturity on NA at maturity were greater than those of nitrogen content, panicle number, growth duration, NAA of leaf, stem and sheath, NAA during transplanting-tillering and tillering-heading. 6) Partial productivity of nitrogen fertilizer (PFPN) was significantly improved in FACE treatment with an average increase of 24.16% and the maximum increment in conventional indica rice. NAA per 100 kg grains was significantly reduced in FACE treatment with an average decrease of 4.7%. The maximum decrease of NAA per 100 kg grains was observed in conventional indica rice varieties.【Conclusion】The results indicated that FACE could markedly increased both grain yield and nitrogen use efficiency in all rice varieties, but the increases varied with the variety types.     

基于三波段光谱指数的春小麦叶片水分含量估算

为探讨利用三波段植被指数（three-band index, 3BI）对春小麦叶片水分含量（leaf water content, LWC）估算的可行性,在田间尺度上,利用ASD-FieldSpec-3光谱仪测定春小麦抽穗期冠层光谱反射率,采用任意波段组合方法,分别建立两波段植被指数（two-band index, 2BI）包括比值植被指数（RVI）、归一化植被指数（NDVI）、差值植被指数（DVI）及3BI,并对单波段反射率、两波段植被指数和三波段植被指数与春小麦抽穗期LWC之间进行相关性分析,筛选稳定的光谱参数,基于人工神经网络（artificial neural network, ANN）、K近邻（K-nearest neighbors, KNN）和支持向量回归（support vector regression, SVR）等3种机器学习算法,建立有效波段组合运算的抽穗期春小麦LWC估算模型,并利用独立样本对模型精度进行检验和评价。结果表明,单波段反射率、2BI和3BI与春小麦抽穗期LWC之间的相关性均达极显著水平（P＜0.01）,而相关系数差异较大,绝对值分别为0.23、0.62、0.94,说明组合波段展现了光谱隐含信息,避免有效光谱信息的丢失;估算模型中,春小麦抽穗期以KNN算法和最佳3BI组合变量（3BI-5_{(1075, 1095, 1085)}、3BI-6_{(1100, 400, 1097)}）构建的模型拟合度最高（r²=0.83）,均方根误差最小（RMSE=2.14%）,相对偏差百分比超出了2.0以上（RPD=2.31）,说明该模型具有一定的预测能力。由此可见,通过任意波段组合,可明显提高3BI与春小麦LWC的关联度,且基于K近邻算法构建的模型具有较好的稳定性和估算能力。